Saudi Aramco (Arabic: ارامكو السعودية ), officially the Saudi Arabian Oil Company, is the national oil company of Saudi Arabia. Saudi Aramco was estimated to be worth $781 billion in 2005, making it the world's most valuable company, and 80% more valuable than ExxonMobil, the 2nd largest public company.

Saudi Aramco has both the largest proven crude oil reserves, at more than 260 billion barrels (4.1×10¹⁰ m³), and largest daily oil production. Headquartered in Dhahran, Saudi Arabia, Saudi Aramco operates the world's largest single hydrocarbon network, the Master Gas System. Its yearly production is 7.9 billion barrels (1.26×10⁹ m³), and it managed over 100 oil and gas fields in Saudi Arabia, including 279 trillion scf of natural gas reserves. Saudi Aramco owns the Ghawar Field, the world's largest oil field, and the Shaybah Field, one of the world's largest oil fields.

The origins of Saudi Aramco can be traced back to May 29, 1933, when the Saudi government granted a concession to Standard Oil of California (Socal) in preference to a rival bid from the Iraq Petroleum Company. The concession allowed Socal to explore for oil in Saudi Arabia. Socal assigned this concession to a wholly owned subsidiary called California-Arabian Standard Oil Co. (Casoc). In 1936, with the company having no success at locating oil, the Texas Oil Company (Texaco) purchased a 50% stake of the concession.